We're starting to get enough calls for 2-photographer events that it's time to stop renting gear for the second shooter (my wife) and get two sets of gear. We currently use the following:
30D
20D
70-200 2.8L IS
24-70 2.8L
Sigma 15-30
...We have extra bodies and a variety of "2nd tier" lenses for backups. When I shoot something myself, I use a belt harness and have the 70-200 on my 20D (shooting ambient light only) and alternate the 24-70 and 15-30 on my 30D which has a stroboframe and a Sigma 500 Flash with a modifier.
Going forward, my wife will shoot with the 20D with a bracket, flash, and modifier, alternating between the 24-70 and the 15-30.
Here's a graph of the percentage of shots from a typical wedding (focal length adjusted for 35mm):

As you can see, I shoot wide with the 15-30 (at 15mm) and at both ends of the 24-70.
I don't really like the 15-30 so much, and I hate to buy another 24-70, since I'm still shooting solo 75% of the time.
I've decided to buy a 5d for the following reasons: better high ISO performance and higher resolution (when you're shooting the typical Orthodox Jewish grandparent, who has 12 children and 12*12 grandchildren, you really need more PPF (pixels per face) than the 30D can provide.
That being the case, I need something with 70mm * 1.6 reach for the 5D. The 135 f/2.0L ($850) will work nicely. To get 15mm * 1.6, I could buy the 24 f/1.4L ($1100). That would be awesome, as I could use as much light as possible for capturing those huge circle dances at Jewish weddings.
Here's the rub: I feel like I need a 30mm * 1.6 to fill the center. The 50mm f/1.4 ($290) would work well, except that it's AF is really bad in low light, and it's realy soft below 2.8. As you can see from the chart, I can use all the light I can get. The other option is to get the 50mm f/1.2L ($1600), but $1600 FOR A 50mm LENS?! ARE YOU OUT OF YOUR MIND?!
So it's $2700 for the 24mm 1.4L and the 50mm 1.2L, or I can spend $1100 and get another 24-70 2.8L. I just hate to have two copies of the same lens. I feel like, with these three primes added to my three zoom lenses, I've really got most combinations covered.
What would you do? Am I crazy spending $1600 on a 50mm lens?
Confused,
-TM